Method of plasma treatment

ABSTRACT

The present invention is a plasma processing method including: a step of introducing a substrate into a processing container, a metal or metallic compound film being formed on a surface of the substrate; a step of supplying a noble gas and an H 2  gas into the processing container; and a step of generating plasma in the processing container while the noble gas and the H 2  gas are supplied, so that a natural oxide film formed on a surface of the metal or metallic compound film is removed by means of the plasma. According to the invention, the noble gas and the H 2  gas are supplied into the processing container, the plasma is generated in the processing container, and the plasma acts on the natural oxide film formed on a surface of the metal or metallic compound film. Thus, active hydrogen in the plasma reduces the natural oxide film, and active species of the noble gas etch the natural oxide film. As a result, the natural oxide film can be removed with a satisfactory selective ratio.

FIELD OF THE INVENTION

[0001] The present invention relates to a plasma processing method thatis used to remove a natural oxide film formed on a metal film or ametallic compound film, in particular on a CoSi₂ film, of a surface of asubstrate.

DESCRIPTION OF THE RELATED ART

[0002] In a semiconductor manufacturing process, a Ti film is depositedon a bottom of a contact hole formed in a silicon wafer as an object tobe processed. A barrier layer such as TiN is formed on a TiSi layer,which is formed by interdiffusion of the Ti film and the silicon wafer.In addition, an Al layer, a W layer, a Cu layer or the like is formed onthe barrier layer. Thereby, filling of the contact hole and forming ofwirings are carried out. Conventionally, a metal-deposition systemhaving a plurality of chambers is used for carrying out the abovesuccessive steps. In such a metal-deposition system, in order to obtaingood electrical contacts, prior to the deposition process, a process forremoving a natural oxide film formed on the silicon wafer, that is, apre-clean process is carried out.

[0003] The pre-clean process is a process wherein plasma of a processgas is generated in a chamber assembled in the metal-deposition systemand wherein the natural oxide film formed on the silicon wafer isremoved by the plasma. According to the pre-clean process, the naturaloxide film can be removed in an in-line manner and relatively easily.

[0004] On the other hand, recently, miniaturization of semiconductordevices has been advanced. For example, if the diameter of a hole is0.15 μm or smaller, it is desired to further lower the resistance ofwiring contact portions. Conventionally, TiSi is used as a material forthe contact portions. Recently, instead of TiSi, a CoSi₂ film, whoseresistance is low, is formed on Si, and then Ti is formed thereon. Inthat case, a natural oxide film may be formed on a surface of the CoSi₂film. The natural oxide film may cause higher resistance of the contactportions. Thus, if a pre-clean process is conducted to efficientlyremove the natural oxide film on the surface of the CoSi₂ film withoutgiving any damage and with a good selective ratio, this is veryadvantageous in the semiconductor manufacturing process.

[0005] However, when the natural oxide film on the CoSi₂ film is removedby the conventional pre-clean process, the etching selective ratio maynot be sufficient. In addition, in a method of removing the naturaloxide film on the CoSi₂ film by means of a process such as a wetprocessing by an HF aqueous solution, the whole exposed surface and thelateral wall of the hole or the like are subjected to an isotropicetching. Thus, it is difficult to use this method for recentminiaturized devices.

[0006] Thus, it is required to achieve a plasma process wherein thenatural oxide film on the CoSi₂ film is efficiently removed with a highselective ratio while less damage is given to the CoSi₂ film.

[0007] In addition, with respect to a natural oxide film on a surface ofany metal or metallic compound film other than the CoSi₂ film as well,if the natural oxide film can be efficiently removed with a highselective ratio by means of a pre-clean process by plasma, this is veryadvantageous in the semiconductor manufacturing process.

SUMMARY OF THE INVENTION

[0008] This invention is developed by focusing the aforementionedproblems in order to resolve them effectively. An object of the presentinvention is to provide a plasma processing method wherein a naturaloxide film on a metal or metallic compound film, in particular a CoSi₂film, can be efficiently removed with a sufficient selective ratio.

[0009] The present invention is a plasma processing method comprising: astep of introducing a substrate into a processing container, a metal ormetallic compound film being formed on a surface of the substrate; astep of supplying a noble gas and an H₂ gas into the processingcontainer; and a step of generating plasma in the processing containerwhile the noble gas and the H₂ gas are supplied, so that a natural oxidefilm formed on a surface of the metal or metallic compound film isremoved by means of the plasma.

[0010] According to the present invention, the noble gas and the H₂ gasare supplied into the processing container, the plasma is generated inthe processing container, and the plasma acts on the natural oxide filmformed on a surface of the metal or metallic compound film. Thus, activehydrogen in the plasma reduces the natural oxide film, and activespecies of the noble gas etch the natural oxide film. As a result, thenatural oxide film can be removed with a satisfactory selective ratio.

[0011] The metal or metallic compound may consist of any of CoSi₂, Co,W, WSi, Cu, Si, Al, Mo, MoSi, Ni and NiSi. It is preferable that anetching selective ratio of the natural oxide film with respect to themetal or metallic compound film is 3 or more.

[0012] It is preferable that the plasma is one of inductive couplingplasma, helicon wave plasma and microwave plasma. Such plasma can begenerated independently from a bias-voltage control of a lower electrodefor drawing-in the plasma. Thus, the natural oxide film can be removedwhile less damage is given to the metal or metallic compound film byions.

[0013] In addition, the present invention is a plasma processing methodcomprising: a step of introducing a substrate into a processingcontainer, a CoSi₂ film being formed on a surface of the substrate; astep of supplying a noble gas and an H₂ gas into the processingcontainer; and a step of generating inductive coupling plasma in theprocessing container and applying a bias voltage to the substrate whilethe noble gas and the H₂ gas are supplied, so that a natural oxide filmformed on a surface of the CoSi₂ film is removed by means of the plasma.

[0014] According to the present invention, the noble gas and the H₂ gasare supplied into the processing container, the inductive couplingplasma is generated in the processing container, and the plasma acts onthe natural oxide film formed on a surface of the CoSi₂ film. Thus,active hydrogen in the plasma reduces the natural oxide film, and activespecies of the noble gas etch the natural oxide film. As a result, thenatural oxide film formed on the surface of the CoSi₂ film can beremoved with a satisfactory selective ratio and without giving anydamage by ions to the CoSi₂ film. In the case, it is preferable that anetching selective ratio of the natural oxide film with respect to theCoSi₂ film is 3 or more.

[0015] Preferably, in the step of supplying a noble gas and an H₂ gasinto the processing container, the H₂ gas is supplied in such a mannerthat an amount of the H₂ gas is 20% or more with respect to a totalamount of the noble gas and the H₂ gas. Further preferably, in the stepof supplying a noble gas and an H₂ gas into the processing container,the H₂ gas is supplied in such a manner that an amount of the H₂ gas is40% or more with respect to a total amount of the noble gas and the H₂gas.

[0016] In addition, preferably, the noble gas is at least one of Ar, Ne,He, Kr and Xe.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic structural view showing a metal-depositionsystem including a pre-clean processing unit wherein a plasma processingmethod according to an embodiment of the present invention is carriedout;

[0018]FIG. 2 is a schematic sectional view of the pre-clean processingunit shown in FIG. 1;

[0019]FIG. 3 is a graph showing a relationship between outputs of ahigh-frequency electric power source and etching selective ratios of anSiO₂ film with respect to a CoSi₂ film;

[0020]FIG. 4 is a graph showing a relationship between ratios of a flowamount of H₂ gas with respect to the total flow amount and etchingselective ratios of an SiO₂ film with respect to a CoSi₂ film; and

[0021]FIG. 5 is a graph showing a relationship between pressures in theprocessing container and etching selective ratios of an SiO₂ film withrespect to a CoSi₂ film.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] Hereinafter, embodiments of the present invention will bedescribed with reference to the attached drawings.

[0023]FIG. 1 is a schematic structural view showing a metal-depositionsystem including a pre-clean processing unit wherein a plasma processingmethod according to an embodiment of the present invention is carriedout. In the metal-deposition system 1, a transfer chamber 10 is arrangedat a central position thereof. Two cassette chambers 11 and 12, adegassing chamber 13, a Ti depositing unit 14, a pre-clean processingunit 15, a TiN depositing unit 16, an Al depositing unit 17 and acooling chamber 18 are provided around the transfer chamber 10. That is,the metal-deposition system 1 is a multi-chamber type of cluster-toolsystem.

[0024] In the metal-deposition system 1, a barrier layer is formed on aCoSi₂ film on a silicon wafer W (hereinafter, which is referred to asmerely a wafer), the silicon wafer W having a contact hole or a viahole, the CoSi₂ film being formed on the hole portion (contact portion).In addition, an Al (aluminum) layer is formed on the barrier layer.Thereby, filling of the hole and forming of an Al wiring are carriedout. Specifically, a single wafer W is taken out from the cassettechamber 11 by means of a transfer arm 19, and then introduced into thepre-clean processing unit 15 through the transfer chamber 10. Thepre-clean processing unit 15 removes a natural oxide film formed on theCoSi₂ film at the contact portion (which is described below in detail).The wafer W is then transferred to the degassing chamber 13 by thetransfer arm 19. A degassing process is carried out to the wafer W inthe degassing chamber 13. Alternatively, without the degassing processin the degassing chamber 13, the wafer W may be directly transferred tothe Ti depositing unit 14.

[0025] Then, the wafer W is introduced into the Ti depositing unit 14.The Ti depositing unit 14 deposits a Ti film on the CoSi₂ film by meansof, for example, a plasma CVD process using an H₂ gas, an Ar gas and aTiCl₄ gas. After the Ti film is deposited, the wafer W is introducedinto the TiN depositing unit 16. The TiN depositing unit 16 deposits aTiN film by means of, for example, a plasma CVD process using an N₂ gasor an NH₃ gas, an Ar gas and a TiCl₄ gas, in order to form a barrierlayer. Alternatively, the TiN film may be deposited by means of athermal CVD process using an N₂ gas, an NH₃ gas and a TiCl₄ gas. Then,the Al depositing unit 17 forms an Al layer on the barrier layer. By theabove steps, a predetermined depositing process is completed. Then, thewafer W is cooled in the cooling chamber 18, and sent to the cassettechamber 12.

[0026] The arrangement of the chambers 14 to 17 is freely determined.The number of respective chambers is determined taking intoconsideration the number of processes to the wafer and throughputthereof. For example, the chambers 14 and 15 may be pre-clean chambers,the chamber 16 may be a Ti depositing chamber, and the chamber 17 may bea TiN depositing chamber. Alternatively, the chamber 14 may be apre-clean chamber, the chambers 15 and 16 may be Ti depositing chambers,and the chamber 17 may be a TiN depositing chamber.

[0027] As described above, a semiconductor device can be manufactured,the semiconductor wafer including, for example, a wafer W having acontact hole reaching an impurity diffusion region and provided with aninterlayer insulating film, a CoSi₂ film formed on the impuritydiffusion zone in the contact hole, a barrier layer formed on the CoSi₂film, and a metal layer formed on the barrier layer to electricallycommunicate with the impurity diffusion region on a substrate.

[0028] In the metal-deposition system 1 of the present embodiment, avacuum state is maintained in the transfer chamber 10. Thus, after thenatural oxide film on the CoSi₂ film is removed by the pre-cleanprocessing unit 15, the wafer W can be subjected to the depositionprocess of the Ti film in the Ti depositing unit 14 without beingexposed to the atmospheric air. That is, a natural oxide film can not beformed again on the CoSi₂ film before the Ti film is deposited. Thereby,the interface between the Ti film deposited by the Ti depositing unit 14and the CoSi₂ film is formed satisfactorily, which may improveelectrical characteristics thereof.

[0029] Next, the pre-clean processing unit 15 included in the abovemetal-deposition system 1 is explained in detail. FIG. 2 is a schematicsectional view of the pre-clean processing unit 15. The pre-cleanprocessing unit 15 is formed as an inductive coupling plasma (ICP)etching unit.

[0030] As shown in FIG. 2, the pre-clean processing unit 15 includes aprocessing container 20 having: a cylindrical chamber 21 that has abottom but whose upper end is open, and a cylindrical bell jar 22 thathas a lid, the bell jar 22 being arranged continuously on the chamber 21via a gas supplying member 45 and a gasket 46.

[0031] In the chamber 21, a susceptor (stage for a substrate) 23 forhorizontally supporting the wafer W as an object to be processed thereonis supported by a cylindrical supporting member 32. A concave portion 24that has substantially the same shape as the wafer W is formed on asurface of a susceptor body 27 of the susceptor 23. The wafer W isadapted to be placed on the concave portion 24. Under the concaveportion 24, a disk-like meshy lower electrode 25 is buried. A biasvoltage may be applied to the lower electrode 25. In addition, a heatingmember 26 consisting of W, Mo or the like is buried below the lowerelectrode 25. The susceptor body 27 consists of an insulating materialsuch as ceramics, for example, AlN, Al₂O₃ or the like. Thus, thesusceptor body 27 and the heating member 26 form a ceramics heater. Adirect-current power source 41 is connected to the heating member 26.When the power source 41 supplies electric power to the heating member26, the heating member 26 is heated and the wafer W may be heated to apredetermined temperature.

[0032] In addition, above the susceptor 23, a circular shadow ring 30made of an insulating material such as quartz, AlN, Al₂O₃ or the like isarranged so as to cover the edge of the wafer W placed on the concaveportion 24. The shadow ring 30 is connected to a circular member 34 viaa supporting pillar 33 that is connected to a lower surface of theshadow ring 30. The circular member 34 is connected to an elevatingmechanism 37 via a rod member 36. When the rod member 36 is moved up anddown by the elevating mechanism 37, the circular member 34, thesupporting pillar 33 and the shadow ring 30 are integrally moved up anddown. The rod member 36 is surrounded by a bellows 35. Thus, it isprevented that the atmosphere in the processing container 20 leaksoutside from a vicinity of the rod member 36.

[0033] The shadow ring 30 have a function to mask the edge of the waferW and a function as a focus ring for generating density-uniform plasmaabove the surface of the wafer W. The shadow ring 30 is moved up to apredetermined position when the wafer W is transferred into the chamber21 and passed onto wafer supporting pins (not shown) that extend throughthe susceptor 23 and can be moved up and down. On the other hand, afterthe wafer W is passed on the wafer supporting pins, when the wafer W isplaced onto the susceptor 23, the shadow ring 30 is moved down togetherwith the wafer supporting pins.

[0034] The above lower electrode 25 is connected to a high-frequencyelectric power source 39 of a frequency of for example 13.56 MHz, via amatching unit 38. When the high-frequency electric power source 39supplies electric power to the lower electrode 25, a predetermined biasvoltage is adapted to be applied to the lower electrode 25 (that is,finally the wafer W).

[0035] The circular gas supplying member 45 and the gasket 46 areprovided between the chamber 21 and the bell jar 22, in order tomaintain airtightness. A plurality of gas-discharging holes is formed inthe gas supplying member 45 at a substantially even arrangement over thewhole circumference thereof. A gas is supplied from a gas supplyingmechanism 60 into the processing container 20 through thegas-discharging holes.

[0036] In addition, an opening 47 is provided in a lateral wall of thechamber 21. A gate valve 48 is mounted at a position corresponding tothe opening 47 outside the chamber 21. Thus, while the gate valve 48 isopened, the wafer W is adapted to be transferred between a load-lockchamber (not shown) and the chamber 21 through the transfer chamber 10.

[0037] The bell jar 22 is made of an electrical insulating material suchas quartz or ceramics. An inductive coil 42 as an antenna, which isplasma generating means, is wound around the outside periphery of thebell jar 22. The coil 42 is connected to a high-frequency electric powersource 44 of a frequency of 450 kHz to 600 MHz, preferably 450 kHz, viaa matching unit 43. When the high-frequency electric power source 44supplies high-frequency electric power to the coil 42 via the matchingunit 43, inductive coupling plasma (ICP) is adapted to be generated inthe bell jar 22.

[0038] The gas supplying mechanism 60 has an Ar gas supplying source 61that supplies an Ar gas, and an H₂ gas supplying source 62 that suppliesan H₂ gas. The Ar gas supplying source 61 is connected to a gas line 63.On the way of the gas line 63, an open-close valve 65, a mass-flowcontroller 67 and an open-close valve 69 are provided in the order. Inaddition, the H₂ gas supplying source 62 is connected to a gas line 64.On the way of the gas line 64, an open-close valve 66, a mass-flowcontroller 68 and an open-close valve 70 are provided in the order. Thegas lines 63, 64 are connected to a gas line 71, and the gas line 71 isconnected to the gas supplying member 45.

[0039] A bottom wall of the chamber 21 is connected to an exhaust pipe50. The exhaust pipe 50 is connected to an exhaust unit 51 including avacuum pump. When the exhaust unit 51 is driven, a vacuum of apredetermined level can be maintained in the processing container 20.

[0040] Then, an operation of removing a natural oxide film formed on awafer W by using the above pre-clean processing unit 15 is explained.

[0041] At first, the gate valve 48 is opened, and a wafer W isintroduced into the chamber 21 by means of the transfer arm 19 providedin the transfer chamber 10 of the metal-deposition system 1. Then, in astate wherein the shadow ring 30 has been moved up, the wafer W ispassed onto the wafer supporting pins (not shown) projecting from thesusceptor 23. Then, the wafer supporting pins and the shadow ring 30 aremoved down, so that the wafer W is placed on the susceptor 23 and theshadow ring 30 masks the outside peripheral edge of the wafer W.

[0042] After that, the gate valve 48 is closed, and the atmosphere inthe processing container 20 is discharged by the exhaust system 51 to apredetermined reduced-pressure state. In the reduced-pressure state, theAr gas and the H₂ gas are introduced at respective predetermined flowrates from the Ar gas supplying source 61 and the H₂ gas supplyingsource 62 into the processing container 20. At the same time, thehigh-frequency electric power source 44 starts to supply high-frequencyelectric power to the coil 42, so that inductive coupling plasma isgenerated in the bell jar 22. Thus, active species of Ar, H₂ and so onare generated. In addition, the high-frequency electric power source 39supplies high-frequency electric power of for example 450 kHz to 60 MHz,preferably 13.56 MHz, to the susceptor 23. That is, a self-bias voltageis applied to the wafer W. This makes it easier for the active speciesto be drawn to the wafer W, that is, the reduction and etching processis more efficiently carried out.

[0043] In the above state, in order to enhance the reduction force, theheating member 26 is heated by electric power from the electric powersource 41 so that the wafer W is heated to 200 to 500° C. Thus, apre-clean process wherein a natural oxide film on a CoSi₂ film formed ata contact portion of the wafer W is reduced, etched and removed iscarried out.

[0044] Then, a gas-discharging amount by the exhaust system 51 andgas-supplying amounts from the Ar gas supplying source 61 and the H₂ gassupplying source 62 are adjusted so that the processing container 20 isreturned to the same vacuum level as the transfer chamber 10. Then, thesupporting pins project from the susceptor 23 to lift up the wafer W.When the gate valve 48 is opened, the transfer arm 19 goes into thechamber 21 and takes out the wafer W. Then, the steps at the pre-cleanprocessing unit 15 are completed.

[0045] According to the above pre-clean process, the natural oxide filmon a CoSi₂ film may be properly removed. In the case, if the ratiobetween the Ar gas as a noble gas and the H₂ gas is properly adjusted,an etching selective ratio of the natural oxide film with respect to theCoSi₂ film can be sufficiently enhanced and damage given to the CoSi₂film as a base layer can be reduced. It is preferable that the etchingselective ratio, that is, a ratio between an etching rate of the CoSi₂film and an etching rate of the natural oxide film is 3 or more.

[0046] In addition, in the present embodiment, inductive electromagneticfield is generated in the bell jar 22, the inductive coupling plasmathat causes less ion-damage to the base layer is generated, and thenatural oxide film is removed by the inductive coupling plasma. Thus,damage by ions to the CoSi₂ film as the base layer can be furtherreduced.

[0047] Regarding the above pre-clean process, experiments were carriedout for investigating effects of process conditions on the etchingselective ratio of the SiO₂ film with respect to the CoSi₂ film. In theexperiments, the process conditions were as follows: the Ar gas flowrate and the H₂ gas flow rate were 0.008 L/min and 0.012 L/min (8 sccmand 12 sccm); the pressure in the processing container 20 was 0.655 Pa;the temperature of the heated wafer W was 500° C.; the electric power ofthe high-frequency electric power source 39 was 200 W; the electricpower of the high-frequency electric power source 44 was 1000 W; and thetime of the pre-clean process was 60 second. While the above values wereused as a reference process condition, any of the output of thehigh-frequency electric power source 39, the H₂ gas flow rate and thepressure in the processing container 20 was variously changed andrespective etching selective ratios of the SiO₂ film with respect to theCoSi₂ film (ratio of SiO₂/CoSi₂) were measured. The results are shown inFIGS. 3 to 5. FIG. 3 is a graph on which the abscissa represents theoutput of the high-frequency electric power source 39 (bias power) andthe ordinate represents the etching selective ratio. FIG. 4 is a graphon which the abscissa represents the ratio of the H₂ gas flow rate withrespect to the total gas flow rate and the ordinate represents theetching selective ratio. FIG. 5 is a graph on which the abscissarepresents the pressure in the processing container 20 and the ordinaterepresents the etching selective ratio.

[0048] Taking into consideration the results of the experiments,preferable process conditions for the pre-clean process are explainedbelow.

[0049] Even if the H₂ gas flow rate supplied into the processingcontainer 20 is very small, if the processing time is short, the naturaloxide film can be removed with less damage to the CoSi₂ film. However,in view of effectively removing the natural oxide film with less damageto the CoSi₂ film, the ratio of the H₂ gas supplied into the processingcontainer 20 is preferably 20% or more, more preferably 40% or more. Inaddition, when the ratio of the H₂ gas is higher, the etching selectiveratio of the natural oxide film is also higher. When the ratio of the H₂gas is 80%, the etching selective ratio of the natural oxide film is 20or more. However, when the ratio of the H₂ gas is higher than 80%, it isdifficult to obtain a desired etched amount (2 nm or more) of thenatural oxide film within a short time. Therefore, it is preferable thatthe ratio of the H₂ gas is not higher than 80%.

[0050] It is preferable that the pressure in the processing container 20is 0.133 to 6.55 Pa (1 to 50 mTorr). More preferably, the pressure is0.133 to 2.66 Pa (1 to 20 mTorr)

[0051] The total flow amount of the gases is 30 sccm or lower,preferably 20 sccm or lower.

[0052] The bias electric power supplied from the high-frequency electricpower source 39 to the susceptor is preferably 20 to 700 W. Morepreferably, it is 100 to 500 W.

[0053] The time of the pre-clean process is preferably 10 to 180 secondin view of etching in-plane uniformity. More preferably, it is 10 to 120second.

[0054] When any process condition satisfying the above ranges isadopted, the natural oxide film formed on the CoSi₂ film can be properlyremoved.

[0055] In addition, the present invention is not limited to the aboveembodiment, but may be variously modified. For example, in the aboveembodiment, the natural oxide film is removed by the inductive couplingplasma. However, this invention is not limited thereto, and helicon waveplasma, microwave plasma such as microwave remote plasma, andhigh-density plasma that may cause less damage by ions can be preferablyused. Of course, any other plasma can be also used. In addition, in theabove embodiment, the natural oxide film on the CoSi₂ film formed on thecontact portion of the wafer W is removed. However, this invention isnot limited thereto, and a natural oxide film formed on a surface of anyother metal or metallic compound film can be removed with a highselective ratio. Such a metal or metallic compound film may be a Cofilm, a W film, a WSi film, a Cu film, a Si film, an Al film, a Mo film,a MoSi film, a Ni film and a NiSi film. In addition, the presentinvention can be also used for removing an oxide formed after apolishing step by means of CMP in a wiring-forming process. In addition,in the above embodiment, the Ar gas is used as a noble gas, but Ne, He,Kr and Xe may be also used.

1. A plasma processing method comprising: a step of introducing asubstrate into a processing container, a metal or metallic compound orSi film being formed on a surface of the substrate, a step of heatingthe substrate to 200 to 500° C., a step of supplying an Ar gas and an H2gas into the processing container, and a step of generating inductivecoupling plasma in the processing container while the Ar gas and the H2gas are supplied, so that a natural oxide film formed on a surface ofthe metal or metallic compound or Si film is removed by the plasma,wherein a total gas flow rate of the Ar gas and the H2 gas is 30 sccm orlower, and an etching selective ratio of the natural oxide film withrespect to the metal or metallic compound or Si film is 3 or more.
 2. Aplasma processing method according to claim 1, wherein in the step ofremoving a natural oxide film, the natural oxide film formed on asurface of the metal or metallic compound or Si film is reduced byactive species of hydrogen and at the same time etched by active speciesof Ar.
 3. A plasma processing method according to claim 1, wherein themetal or metallic compound consists of any of CoSi₂, Co, W, Wsi, Cu, Al,Mo, MoSi, Ni and NiSi. 4-6. (Canceled).
 7. A plasma processing methodcomprising: a step of introducing a substrate into a processingcontainer, a CoSi₂ film being formed on a surface of the substrate, astep of supplying an Ar gas and an H₂ gas into the processing container,and a step of heating the substrate to 200 to 500° C., a step ofgenerating inductive coupling plasma in the processing container andapplying a high-frequency bias voltage to the substrate while the Ar gasand the H₂ gas are supplied, so that a natural oxide film formed on asurface of the CoSi₂ film is removed by the plasma, wherein a total gasflow rate of the Ar gas and the H₂ gas is 30 sccm or lower, and anetching selective ratio of the natural oxide film with respect to themetal or metallic compound or Si film is 3 or more.
 8. A plasmaprocessing method according to claim 7, wherein in the step of removinga natural oxide film, the natural oxide film formed on a surface of theCoSi₂ film is reduced by active species of hydrogen and at the same timeetched by active species of Ar.
 9. (Canceled).
 10. A plasma processingmethod according to claim 1 or 7, wherein in the step of supplying an Argas and an H₂ gas into the processing container, the H₂ gas is suppliedin such a manner that a flow rate of the H₂ gas is 20% or more withrespect to a total gas flow rate.
 11. A plasma processing methodaccording to claim 10, wherein in the step of supplying an Ar gas and anH₂ gas into the processing container, the H₂ gas is supplied in such amanner that a flow rate of the H₂ gas is 40% or more with respect to atotal gas flow rate.
 12. (Canceled).
 13. A plasma processing methodaccording to claim 1, wherein a frequency for generating the inductivecoupling plasma is 450 kHz to 60 MHz, and a frequency of thehigh-frequency bias voltage is 13.56 MHz.
 14. A plasma processing methodaccording to claim 1, wherein a pressure in the processing container is0.133 to 6.55 Pa.
 15. A plasma processing method according to claim 14,wherein the pressure in the processing container is 0.133 to 2.66 Pa.16. (Canceled).
 17. A plasma processing method according to claim 1 or7, wherein the total gas flow rate of the Ar gas and the H₂ gas is 20sccm or lower. 18-19. (Canceled).
 20. A plasma processing methodaccording to claim 1, wherein the time of the step of removing thenatural oxide film is 10 to 180 seconds.
 21. A plasma processing methodaccording to claim 20, wherein the time of the step of removing thenatural oxide film is 10 to 120 seconds.
 22. A plasma processing methodfor removing a natural oxide film formed on a substrate, by usinginductive coupling plasma, with a high selective ratio with respect tothe substrate, without giving any damage to the substrate, the methodcomprising: a step of placing a substrate on a susceptor arranged in aprocessing container, a step of masking an edge of the substrate, a stepof adjusting a pressure in the processing container to a predeterminedpressure, by supplying an H₂ gas and a noble gas into the processingcontainer at predetermined rates, a step of applying a predeterminedbias voltage to the substrate via the susceptor, by supplyinghigh-frequency electric power to a lower electrode buried in thesusceptor, a step of heating the substrate to 200 to 500° C., and a stepof generating plasma of the H₂ gas and the noble gas in the processingcontainer, so that a natural oxide film formed on the substrate isremoved with a high selective ratio with respect to the substrate,without giving any ion-damage to the substrate, wherein a total gas flowrate of the noble gas and the H₂ gas is 30 sccm or lower, and the highselective ratio is 3 or more.
 23. A plasma processing method accordingto claim 22, wherein in the step of adjusting a pressure in theprocessing container to a predetermined pressure by supplying an H₂ gasand a noble gas into the processing container at a predetermined rates,the H₂ gas is supplied at a rate of 20% or more with respect to a totalgas flow rate.
 24. A plasma processing method according to claim 23,wherein in the step of adjusting a pressure in the processing containerto a predetermined pressure by supplying an H₂ gas and a noble gas intothe processing container at predetermined rates, the H₂ gas is suppliedat a rate of 40% or more with respect to a total gas flow rate. 25.(Canceled).
 26. A plasma processing method according to claim 22,wherein the noble gas is one of Ar, Ne, He, Kr and Xe.
 27. (Canceled).28. A plasma processing method according to claim 22, wherein any of Co,W, Wsi, Cu, Si, Al, Mo, MoSi, Ni and NiSi has been formed on a surfaceof the substrate. 29-34. (Canceled).
 35. A plasma processing methodcomprising: a step of introducing a substrate into a processingcontainer, a metal or metallic compound or Si film being formed on asurface of the substrate, a step of supplying an Ar gas and an H₂ gasinto the processing container, and a step of generating inductivecoupling plasma in the processing container while the Ar gas and the H₂gas are supplied, so that a natural oxide film formed on a surface ofthe metal or metallic compound or Si film is removed by the plasma,wherein a total gas flow rate of the Ar gas and the H₂ gas is 30 sccm orlower, and an etching selective ratio of the natural oxide film withrespect to the metal or metallic compound or Si film is 3 or more.
 36. Aplasma processing method comprising: a step of introducing a substrateinto a processing container, a CoSi₂ film being formed on a surface ofthe substrate, a step of supplying an Ar gas and an H₂ gas into theprocessing container, and a step of generating inductive coupling plasmain the processing container and applying a high-frequency bias voltageto the substrate while the Ar gas and the H₂ gas supplied, so that anatural oxide film formed on a surface of the Cosi₂ film is removed bythe plasma, wherein a total gas flow rate of the Ar gas and the H₂ gasis 30 sccm or lower, and an etching selective ratio of the natural oxidefilm with respect to the metal or metallic compound or Si film is 3 ormore.
 37. A plasma processing method for removing a natural oxide filmformed on a substrate, by using inductive coupling plasma, with a highselective ratio with respect to the substrate, without giving any damageto the substrate, the method comprising: a step of placing a substrateon a susceptor arranged in a processing container, a step of masking anedge of the substrate, a step of adjusting a pressure in the processingcontainer to a predetermined pressure, by supplying an H₂ gas and anoble gas into the processing container at predetermined rates, a stepof applying a predetermined bias voltage to the substrate via thesusceptor, by supplying high-frequency electric power to a lowerelectrode buried in the susceptor, and a step of generating plasma ofthe H₂ gas and the noble gas in the processing container, so that anatural oxide film formed on the substrate is removed with a highselective ratio with respect to the substrate, without giving anyion-damage to the substrate, wherein a total gas flow rate of the noblegas and the H₂ gas is 30 sccm or lower, and the high selective ratio is3 or more.
 38. A plasma processing method according to claim 7, whereina frequency for generating the inductive coupling plasma is 450 kHz to60 MHz, and a frequency of the high-frequency bias voltage is 13.56 MHz.39. A plasma processing method according to claim 7, wherein a pressurein the processing container is 0.133 to 6.55 Pa.
 40. A plasma processingmethod according to claim 7, wherein the time of the step of removingthe natural oxide film is 10 to 180 seconds.